ASTM_D_1685_-_05.pdf

Designation:D 1685-05WTER:NATIONALStandard Test Method forTraces of Thiophene in Benzene by SpectrophotometryThis standard is issued under the fixed designation D 1685;the number ummediately following the designatnion undicates the year oforiginal adopton or,in the case of revision,the year of last revision A number in parentheses indicates the year of last reapproval.Asuperscript epsilon(e)indicates an editorial change since the last revision or reapproval.1.Scope*D 4790 Terminology of Aromatic Hydrocarbons and Re-1.1 This test method covers the determination of thiophenelated Chemicalsin benzene in which the thiophene concentration is between 0.1D 6809 Guide for Quality Control and Quality Assuranceand 250 mg/kg.Procedures for Aromatic Hydrocarbons and Related Ma-1.2 Contaminating materials that are darkened by sulfuricterialsacid interfere and must be compensated for by a sample blankE29 Practice for Using Significant Digits in Test Data todetermination.Neither carbon disulfide in concentrations asDetermine Conformance with Specificationshigh as 100 mg/kg nor water as high as the level of saturationE 832 Specification for Laboratory Filter Paperswill interfere.2.2 Other Document:1.3 Contaminating materials may occasionally cause theOSHA Regulations,29 CFR,paragraphs 1910.1000 andcolor development in this test method to be time dependent and1910.12003may also contribute to spectral interferences at 589 nm.3.TerminologyConsequently,test results indicating substantial thiophene,thatcannot be verified by total sulfur analysis,should be considered3.1 Definitions:suspect.3.1.1 For definition of terms used in this test method see1.4 In determining the conformance of the test results usingTerminology D 4790.this method to applicable specifications,results shall be4.Summary of Test Methodrounded off in accordance with the rounding-off method ofPractice E 29.4.1 Thiophene is reacted with isatin,under prescribed con-1.5 The values stated in SI units are to be regarded asditions,to form a colored compound.The compound isstandard.No other units of measurement are included in thisextracted into sulfuric acid,and the intensity of the color isstandard.measured spectrophotometrically.Thiophene concentration is1.6 This standard does not purport to address all of theobtained by correlation with knowns.safery concems,if any,associated with its use.It is the5.Significance and Useresponsibility of the user of this standard to establish appro-priate safety and health practices and determine the applica-5.1 This test method is suitable for setting specifications onbility of regulatory limitations prior to use.For specific hazardbenzene and for use as an internal quality control tool wherestatements,see 7.6,8.1,and 9.1.benzene is either produced or used in a manufacturing process.It may also be used in development or research work involving2.Referenced Documentsbenzene.2.1 ASTM Standards:26.ApparatusD 1193 Specification for Reagent WaterD 3437 Practice for Sampling and Handling Liquid CyclicNoTE 1-Labware made from matenals other than glass and is imper-Productsvious to the materials used in this standard is allowed.6.1 Separatory Funnels,50,250,500,and 1000-mL,withstoppers.6.2 Spectrophotometer-Any spectrophotometer may beThis test method is under the junsdiction of ASTM Commuttee D16 onused that is capable of repeatability of 0.005 absorbance unitsAromanc Hydrocarbons and Related Chemucals and is the direct responsibiiity ofSubcommittee D16.01 on Benzene,Toluene,Xylene,Cyclohexane,and Theirin the range from 0.1 to 1.4 absorbance and repeatability ofDenvanves.wavelength of 1 nm in the region from 400 to 700 nm.Current editon approved July 1,2005.Publhished August 2005 Ornginally6.3 Absorption Cells,1-cm,matched,glass or silica.approved in 1958 Last previous edinion approved in 2000 as D 1685-00.2 For referenced ASTM standards,visit the ASTM website,www.astm org,orcontact ASTM Customer Service at serviceastm.org.For Annual Book of ASTMStandards volume information,refer to the standards Document Summary page on Available from U S.Government Printing Office Supenntendent of Documents,the ASTM website.732 N Capitol St,NW,Mail Stop.SDE,Washington DC 20401.*A Summary of Changes section appears at the end of this standard.Copynght ASTM Intematonal,100 Barr Harbor Dnve,PO Box C700,West Conshohocken,PA 19428-2959,Unrted States3224D1685-056.4 Analyrical Balance,capable of measuring 0.1 mg7.7 Isatin,Chloroform,Benzene Solution-Add 0.5 g of6.5 Pipets,1,2,5,and 10-mL.isatin to 200 mL of chloroform.Heat,in a fume hood,to a6.6 Graduated Cylinders,250 and 1000-mL.temperature just below the boiling point(61C)of chloroform6.7 Volumetric Flasks,stoppered,50,100,250,and 1000-and maintain for 5 min with stirring.Filter into a 250-mLmL.volumetric flask through hardened rapid filter paper.Wash the6.8 Filter Papers:filter paper with two 20-mL portions of thiophene-free benzene6.8.1 Medium-Particle Retention:11 um;Porosity:Me-(from 7.5)eluting the washings into the volumetric flask.dium;Filtration Speed;Specification E 832,40 seconds:Sur-Dilute to volume with thiophene-free benzene.face:Smooth.7.8 Thiophene-99%.6.8.2 Rapid hardened-Particle Retention:20 to 25 um;Porosity:Coarse;Filtration Speed:Specification E832,108.Hazardsseconds;Surface:Smooth,hard.8.1 Consult current OSHA regulations and suppliers Mate-rial Safety Data Sheets for all materials used in this test7.Reagents 4method.7.1 Purity of Reagents-Reagent grade chemicals shall beused in all tests.Unless otherwise indicated,it is intended that9.Samplingall reagents shall conform to the specifications of the Commit-9.1 Sampling of benzene should follow safe rules in order totee on Analytical Reagents of the American Chemical Society,adhere to all safety precautions as outlined in the latest OSHAwhere such specifications are available.s Other grades may beregulations.Refer to Practice D 3437 for proper sampling andused,provided it is first ascertained that the reagent is ofhandling of benzenesufficiently high purity to permit its use without lessening theaccuracy of the determination.10.Preparation of Reagent Blanks and Sample Blank 47.2 Puriry of Water-Unless otherwise indicated,references10.1 Reagent Blank 1-To a 50-mL separatory funnel pipetto water shall be understood to mean Type IV reagent water5 mL of isatin solution and 10 mL of ferric sulfate-sulfuric acidconforming to Specification D 1193.solution.Stopper and shake for 2 min15 s.The shaking is7.3 Cadmium Chloride Solution(20 g/L)-Dissolve 20 g ofaccomplished by wrist action in a rocking motion through aanhydrous cadmium chloride(CdCl2)or 25 g of cadmium180 arc roughly once each second.Allow the two phases tochloride hydrate(CdCl,21 H2O)in 200 mL of water andseparate and draw off the lower HSO layer into a 50-mLdilute to】L.volumetric flask.Add 10 mL of H2SO to the separatory7.4 Sulfuric Acid(sp gr 1.84)-Concentrated H2SO4.funnel,stopper,and shake for 305 s.Again draw off the7.5 Benzene,Thiophene-Free:lower H2SO layer into the 50-mL volumetric flask containing7.5.1 Wash 700 mL of benzene in a 1000-mL separatorythe first extract.Dilute to volume with H 2SO and mix.Thisfunnel with successive 100-mL portions of concentrated sul-blank is stable for 8 h and need not be repeated with eachfuric acid(H 2SO)to which has been added 5 mL of isatinanalysis during this period.solution,until the HSO layer is light yellow or colorless.10.2 Reagent Blank 2-Into a 50-mL volumetric flask,pipetWash the benzene with 100 mL of water and then twice with10 mL of ferric sulfate-sulfuric acid solution and dilute to100 mL of cadmium chloride solution(CdCl2).Finally,washvolume with H2SO.Stopper and mix.This blank is stable forwith another 100-mL portion of water.Filter the benzene8 h and need not be repeated with each analysis during thisthrough medium filter paper into a storage bottle and tightlyperiod.stopper.10.3 Sample Blank-Take a 100-mL portion of the CdCl27.5.2 Prepare 1400 mL of thiophene-free benzene.Measurewashed and filtered benzene sample(prepared in accordancethe absorbance of this material by the procedure outlined inwith the procedure in 12.1).Transfer to a 250-mL separatory11.2 and 12.2.The absorbance should be no greater than 0.01.funnel.Add 10 mL of ferric sulfate-sulfuric acid solution,7.6 Ferric Sulfate,Sulfuric Acid Solution-Add 0.2 g ofstopper,and shake for 2 min15 s.Allow the two phases toferric sulfate(Fe2(SO4)39H2O)together with 38 mL of waterseparate and draw off the lower H2SO layer into a 50-mLto a 1-L volumetric flask.Swirl to dissolve.Cautiously addvolumetric flask.Add 10 mL of H2SO to the separatory funnelabout 100 mL of H2SO and swirl.Allow time for the heat ofand shake for 30 5 s.Again draw off the lower HSO.layerreaction to subside and dilute to volume with HSO.into the 50-mL volumetric flask containing the first extract.(Warning-Appropriate personal protective equipment shouldDilute to volume and mix.Repeat with each specimen.be worn(for example,face shields,goggles,etc.)wheneverconcentrated sulfuric acid(HSO)is used.)11.Preparation of Calibration Curves 4Nore 2-The use of purchased solutions is allowed.The user of thisAlterate volumes of solutons may be prepared providing the speeifiedstandard assumes the responsibility of ensuring solutions or standards areconcentrations are met and there is adequate volume to accurately perform the test.prepared with matenals that meet the requirements expressed in theReagent Chemicals,Amencan Chemcal Soctety Specificatons,AmencanReagents section of this standard.Additionally.the user of this standardChemical Soctety,Washington,DC.For suggestions on the testing of reagents notassumes the responsibility of ensuring any purchased solutions or stan-listed by the Amencan Chemucal Socety,see Analar Standards for Laboratorydards are prepared as expressed in this standard.Chenucals,BDH L.,Poole,Dorset,U.K,and the United States Pharmacopetaand Nenonal Formulary,U.S.Pharmacopeial Convention,Inc.(USPC),Rockville,11.1 Add approximately 0.2 g of thiophene,weighed to theMD.nearest 0.0002 g to a 100-mL volumetric flask containing about323